Synthesis and structure of hydrazones obtained by the reaction of 2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-tetrahydropyrimidin-3-yl]acetic acide hydrazide with β-dicarbonyl compounds

Article abstract of DOI:10.1134/S1070428014050157

Reaction of 2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4- tetrahydropyrimidin-3-yl]acetic acid hydrazide with β-dicarbonyl compounds proceeds regioselectively; the structure of the formed hydrazones is governed by the structure of the β-dicarbonyl reaction component. The reaction with acetyl- and propionylacetone afforded 3-[2-(5-alkyl-3-methyl-1H-pyrazol-1-yl)-2- oxoethyl]-6-methyl-1-(thietan-3-yl)pyrimidin-2,4(1H,3H)-diones, with aroylacetones, 5-hydroxypyrazoline derivatives which are present in DMSO solutions in E′ conformation with respect to the amide bond. The condensation products with acetoacetic acid derivatives have a linear structure and consist of mixtures of E,Z- and E′,Z′-isomers owing to the geometric and conformational isomerism.

Full text of DOI:10.1134/S1070428014050157

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 5, pp. 711–715. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © S.A. Meshcheryakova, V.A. Kataev, 2014, published in Zhurnal Organicheskoi Khimii, 2014, Vol. 50, No. 5, pp. 722–726.
Synthesis and Structure of Hydrazones Obtained by the Reaction
of 2-[6-Methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-
tetrahydropyrimidin-3-yl]acetic
Acide Hydrazide with β-Dicarbonyl Compounds
S. A. Meshcheryakova and V. A. Kataev
Bashkir State Medical University, ul. Lenina 3, Ufa, 45000 Russia
е-mail: centreles@mail.ru
Received October 11, 2013
Abstract—Reaction of 2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-tetrahydropyrimidin-3-yl]acetic acid
hydrazide with β-dicarbonyl compounds proceeds regioselectively; the structure of the formed hydrazones is
governed by the structure of the β-dicarbonyl reaction component. The reaction with acetyl- and
propionylacetone afforded 3-[2-(5-alkyl-3-methyl-1Н-pyrazol-1-yl)-2-oxoethyl]-6-methyl-1-(thietan-3-yl)pyri-
midin-2,4(1Н,3Н)-diones, with aroylacetones, 5-hydroxypyrazoline derivatives which are present in DMSO
solutions in E' conformation with respect to the amide bond. The condensation products with acetoacetic acid
derivatives have a linear structure and consist of mixtures of Е,Z- and E',Z'-isomers owing to the geometric
and conformational isomerism.
DOI: 10.1134/S1070428014050157
Reactions of acid hydrazides with β-dicarbonyl
compounds depending on the structures of the N-acyl
substituent in the hydrazine component and on the β-
dicarbonyl reagent lead to the formation of derivatives
with pyrazole, 5-hydroxypyrazoline, or enhydrazine
structures [1–6]. We report here on the reactions of
previously unknown 2-[6-methyl-2,4-dioxo-1-(thietan-
3-yl)-1,2,3,4-tetrahydropyrimidin-3-yl]acetic acid hyd-
razide with β-dicarbonyl compounds: acylacetones of
aliphatic and aromatic acids, acetoacetic acid derivatives.
chloroacetate in the presence of potassium carbonate in
acetone followed by the condensation of the obtained
ester II with hydrazine hydrate (Scheme 1). The Н
1
NMR spectrum of hydrazide III in DMSO-d6 shows
that in the solution the hydrazide exists as a mixture of
Е,Z-isomers due to the hindered rotation around the
hydrazide N–C bond. The sterically more stable Z-
isomer prevails; the signals of groups СН2СО of the
acetic acid residue and NН2 of the hydrazine residue in
the spectrum are shifted upfield by 0.37 and 0.25 ppm
respectively, and the signals of the hydrazide proton
NН, of the methyl group, and the proton in the position
5 of the uracyl fragment are displaced downfield by
0.59, 0.06, and 0.02 ppm respectively.
2-[6-Methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-tetra-
hydropyrimidin-3-yl]acetic acid hydrazide (III) was
obtained by alkylating compound I with ethyl
Scheme 1.
O
N
O
N
O
N
OEt
Cl
NH
OEt
N2H4 H2O
N
NH2
NH
N
O
O
K2CO3
O
Me
O
Me
O
Me
O
S
S
S
I
II
III
711

MESHCHERYAKOVA, KATAEV
712
Scheme 2.
Me
Me
O
O
N
N
N
N
N
N
R
HO
O
O
R
Me
N
S
O
Me
N
S
O
Me
R
III
+
A
IV a, IV b
O
O
Me
O
N
N
N
R
HO
O
Me
N
S
O
Va_Vc
IV, R = Me (a), Et (b); V, R = Ph (a), 4-ClC6H4 (b), 4-BrC6H4 (c).
The regiodirection of the reaction between
hydrazide III and various β-dicarbonyl compounds in
ethanol without acid catalysts depends on the structure
of the β-dicarbonyl component of the reaction. For
instance, from the reaction with acetyl- and
propionylacetone we isolated N-acylpyrazoles IVа and
IVb in 69–71% yield (Scheme 2).
around the N–CO and N–N bonds. In order to establish
the structure of the synthesized hydrazones we have
selected as model compounds cyclic hydrazones where
both the geometric isomerism and the rotation around
N–N bond are excluded, and the only characteristic
feature is the conformational isomerism due to the
hindered rotation around the hydrazide N–C bond [2, 3].
1
The presence in the Н NMR spectra of compounds
1Н NMR spectra of compounds IVа and IVb
confirm the formation of the pyrazole: along with the
signals of the protons of 6-methylthietanylpyrimidine
and СН2 group of the acyl substituent a characteristic
singlet signal is observed at δ 6.30 (IVа) and 6.45 ppm
(IVb) belonging to the =СН proton of the pyrazole
ring. The protons of methyl groups of pyrazole IVа
give rise to two singlets at δ 2.19 and 2.47 ppm, and
the proton signal of the methyl group in the position 3'
is located upfield with respect to the analogous signal
from the group in the position 5' [7]. The presence of a
singlet from the protons of the methyl group of
pyrazole IVb in the upfield region at δ 2.01 ppm
indicates that in the case of unsymmetrical β-diketone,
propionylacetone, 3-methyl-5-ethylpyrazole system is
obtained.
IVа and IVb of a single set of signals and a singlet
from the protons of the СН2СО group in the more
downfield region (δ 5.35 and 4.85 ppm respectively)
shows that the N-acylpyrazoles IVа and IVb exist in a
single stereoisomeric form of Е'-conformation [2–4].
This is due to the existence in compounds IVа and
IVb like in the other acylhydrazones of a system of π-
р-π-conjugation in a coplanar fragment С=N-N¨–С=О,
and the dipole-dipole repulsion of the oxygen atom and
the imine nitrogen atom makes impossible the
formation of the alternative Z'-conformer [2, 3].
1Н NMR spectra of the condensation products of
hydrazide III with aroylacetones also contain a single
set of resonances, confirming the regioselectivity of
the reaction, but the examination of these spectra
shows that compounds Vа–Vc have the 5-hydroxy-
pyrazoline structure (Scheme 2). Analogously to the
data [4], the dehydration of hydroxypyrazolines Vа–
Vc under the present conditions is impeded by the –I-
effect of the phenyl substituent whereas the alkyl
Acylhydrazones may exist in the form of four
stereoisomers due to the geometric isomerism (E,Z)
with respect to the С=N bond and the conformational
isomerism (E',Z') owing to the hindered rotation
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SYNTHESIS AND STRUCTURE OF HYDRAZONES
713
substituents in the acylacetones possessing the +I-
effect facilitate the dehydration, and the reaction does
not stop at the stage 1-acyl-5-hydroxypyrazolines А
and proceeds with the formation of 1-acyl-pyrazoles
IVа and IVb (Scheme 2).
the polar solvent DMSO-d6 capable of forming inter-
molecular hydrogen bonds with acyl-hydrazones both
in the E'- and the Z'-configurations the isomer prevails
that is less prone to self-association [3, 6]. The spectra
of compounds VIа and VIb confirm that the
equilibrium of the obtained hydrazones in DMSO-d6
solution is shifted in the direction of the Е,Е'-isomer,
therefore the Z'-conformer in this case is more prone to
self-association. The chemical shifts of protons of
СН2СО and NН groups of Е,E'-isomer of compounds
VIа and VIb are observed in a weaker field, and the
proton signals of the СН3С=N group, in a stronger
field as compared with the corresponding signals of the
Е,Z'-isomer in agreement with the published data [2–4, 6].
In the spectra of compounds Vа–Vc the proton
signal of the СН2 group of the pyrazoline system is
overlapped by the pseudotriplet of protons of one of
the S(CH)2 groups from the thietane ring; as a result a
combined multiplet is registered in the region δ 3.03–
3.18 ppm with the intensity corresponding to four
protons. The singlet signal at δ 7.03–7.17 ppm belongs
to the proton of the hydroxy group whose location is
typical of the OH group proton involved in the
formation of a strongly conjugated intramolecular
hydrogen bond with a carbonyl group and confirms the
exclusively Е'-conformation structure with respect the
hydrazide bond [5, 6] in 5-hydroxypyrazolines Vа–Vc
dissolved in DMSO-d6. The presence in the spectra of
compounds Vа–Vc of the signals of methyl group
protons in the stronger field at 2.04 or 2.05 ppm shows
as in the case of compound IVb that the condensation
occurs at the carbonyl function contiguous to the
methyl group.
The third observed set of signals corresponds to the
Z-isomer with the E'-conformational structure with
respect to the hydrazide bond. The signal of the
protons of the methyl group at the С=N bond of the
Z,Е'-isomers of compounds VIа and VIb is registered
in a weaker field as compared with the signal of Е,Е'-
isomer [2], as well as the proton signals of NН and
СН2СО groups. The stabilization of the Z-isomer may
be ascribed to the formation of an intramolecular
hydrogen bond between the NН group of the hyd-
razone fragment and the carboxy group in the ylidene
fragment of acylhydrazones VIа and VIb [8]. Because
of the small proportion in the mixture of the Z'-
conformer the Z,Z'-stereoisomer was not detected in
the spectra.
Reactions of hydrazide III with ethyl acetoacetate
and 2-benzyl-3-oxobutanoic acid led to the formation
of compounds VIа and VIb with a linear hydrazone
structure (Scheme 3) proved by the NMR data.
In the 1Н NMR spectra of compounds VIа and VIb
in DMSO-d6 three sets of signals were observed
showing the existence of geometric and conforma-
tional isomerism. The predominant isomer is the more
stable Е-isomer with the anti-location of the hydrazine
and acetyl residues existing as a mixture of two
stereoisomers owing to the hindered rotation around
the N–CO bond, as shows the doubling of proton
signals of groups СН2СО, NН, СН3С=N, and the
methyl group of the uracyl fragment [2]. As known, in
Hence the reactions of hydrazide III with β-di-
carbonyl compounds proceed regioselectively ex-
clusively at the acetyl function and result in the
formation of products with cyclic or linear structure.
N-Acylpyrazoles, the products of the reaction with
alkyl-containing β-diketones, and N-acyl-5-hydroxy-
pyrazolines, the condensation products with aroyl-
acetones, exist in DMSO-d6 solution in a single Е'-
stereoisomeric form. With the derivatives of aceto-
Scheme 3.
O
Me
O
H
R
N
N
N
X
Me
X
III
+
O
R
Me
N
S
O
O
O
VI a, VIb
R = H, X = OEt (a); R = Bn, X = OH (b).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 5 2014

MESHCHERYAKOVA, KATAEV
714
acetic acid hydrazones of linear structure are formed as
a mixture of Е,Z'-, Е,Е'-, and Z,Е'-isomers with the
prevalence of Е'-conformer.
3-[2-(3,5-Dimethyl-1Н-pyrazol-1-yl)-2-oxoethyl]-
6-methyl-1-(thietan-3-yl)pyrimidine-2,4(1Н,3Н)-
dione (IVа). To a solution of 0.54 g (2 mmol) of
compound III in 15 mL of EtOH was added 0.8 g
(8 mmol) of acetylacetone. The reaction mixture was
boiled for 3 h, cooled, the precipitate was filtered off,
washed with EtOH, and dried. Yield 0.46 g (69%),
EXPERIMENTAL
1Н NMR spectra were registered on spectrometers
Bruker АMХ-300 (operating frequency 300 MHz),
Bruker Avance III-500 (operating frequency 500.13 MHz).
The signals of residual protons of solvent DMSO-d6
served as internal reference. TLC was carried out on
Silufix plates, eluent ethyl acetate or ethanol,
development under UV irradiation or in iodine vapor.
1
white crystals, mp 179–181ºС (i-PrOH). Н NMR
spectrum (300 MHz), δ, ppm: 2.19 s (3Н, 3'-СН3),
2.24 s (3Н, 6-СН3), 2.47 s (3Н, 5'-СН3), 3.09–3.14 m
[2Н, S(CH)2], 4.13–4.19 m [2Н, S(CH)2], 5.35 s (2Н,
3-СН2СО), 5.73 s (1Н, Н5), 6.02–6.08 m (1Н, NCH),
6.30 s (1Н, Н4'). Found, %: С 54.01; Н 5.25; N 16.66.
С15Н18N4О3S. Calculated, %: С 53.88; Н 5.43; N 16.75.
6-Methyl-1-(thietan-3-yl)pyrimidine-2,4(1Н,3Н)-
dione (I) was obtained by procedure [9].
Compounds IVb, VIа and VIb were prepared
similarly.
Ethyl 2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-
tetrahydropyrimidin-3-yl]acetate (II). A slurry of
4.0 g (20 mmol) of compound I and 4.14 g (30 mmol)
of calcined finely ground potassium carbonate in
125 mL of acetone was boiled for 30 min, then 2.45 g
(20 mmol) of ethyl chloroacetate was added, 2 h later
more 1.23 g (10 mmol) of ethyl chloroacetate was
added, and the reaction mixture was boiled for 5 h,
cooled, the precipitate was filtered off. The filtrate was
evaporated in a vacuum, the residue was recrystallized
from hexane. Yield 4.24 g (74%), white crystals, mp
3-[2-(3-Methyl-5-ethyl-1Н-pyrazol-1-yl)-2-oxo-ethyl]-6-
methyl-1-(thietan-3-yl)pyrimidine-2,4(1Н,3Н)-dione
(IVb). Yield 0.49 g (71%), white crystals, mp 173–
175ºС (PrOH). 1Н NMR spectrum (300 MHz), δ, ppm:
0.77 t (3Н, 5'-СН2СН3, J 7.3 Hz), 2.01 s (3Н, 3'-СН3),
2.11 s (3Н, 6-СН3), 3.05–3.13 m [4Н, 5'-СН2СН3, S
(CH)2], 4.15–4.21 m [2Н, S(CH)2], 4.85 s (2Н, 3-
СН2СО), 5.66 s (1Н, Н5), 6.03–6.09 m (1Н, NCH),
6.45 s (1Н, Н4'). Found, %: С 55.22; Н 5.73; N 16.14.
С16Н20N4О3S. Calculated, %: С 55.15; Н 5.78; N 16.08.
1
40–42ºС. Н NMR spectrum (500 MHz), δ, ppm:
3-[2-(5-Hydroxy-3-methyl-5-phenyl-4,5-dihydro-
1Н-pyrazol-1-yl)-2-oxoethyl]-6-methyl-1-(thietan-3-
yl)pyrimidine-2,4(1Н,3Н)-dione (Vа). To a solution
of 0.54 g (2 mmol) of compound III in 15 mL of EtOH
was added 0.65 g (4 mmol) of benzoylacetone. The
reaction mixture was boiled for 3 h, cooled, the
precipitate was filtered off, washed with EtOH, and
dried. Yield 0.53 g (64%), white crystals, mp 159–
1.27 t (3Н, ОСН2СН3, J 7.1 Hz), 2.17 s (3Н, 6-СН3),
3.10–3.14 m [2Н, S(CH)2], 4.12–4.16 m [2Н, S(CH)2],
4.25 q (2Н, ОСН2СН3, J 7.1 Hz), 4.62 s (2Н, 3-
СН2СО), 5.69 s (1Н, Н5), 6.02–6.08 m (1Н, NCH).
Found, %: С 50.81; Н 5.59; N 9.97. С12Н16N2О4S.
Calculated, %: С 50.69; Н 5.67; N 9.85.
2-[6-Methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-
tetrahydropyrimidin-3-yl]acetic acid hydrazide (III).
To a solution of 2.84 g (10 mmol) of compound II in
50 mL of ethanol was added 2.94 g (50 mmol) of 85%
solution of hydrazine hydrate, and the mixture was
boiled for 3 h. The reaction mixture was maintained at
0ºС over 12 h, the precipitate was filtered off, washed
with water, and dried. Yield 1.43 g (53%), white
1
161°С (i-PrOH). Н NMR spectrum (300 MHz), δ,
ppm: 2.05 s (3Н, 3'-СН3), 2.07 s (3Н, 6-СН3), 3.04–
3.18 m [4Н, С4'Н2, S(CH)2], 4.11–4.19 m [2Н, S(CH)2],
4.93 s (2Н, 3-СН2СО), 5.61 s (1Н, Н5), 6.00–6.06 m
(1Н, NCH), 7.03 s (1Н, 5'-ОН), 7.24–7.37 m (5Нarom).
Found, %: С 58.12; Н 5.31; N 13.57. С20Н22N4О4S.
Calculated, %: С 57.95; Н 5.35; N 13.52.
1
crystals, mp 199–201ºС (EtOH). Н NMR spectrum
Compounds Vb and Vc were analogously obtained.
(500 MHz), δ, ppm: 2.08 (Е), 2.14 (Z) s (3Н, 6-СН3),
3.07–3.11 m [2Н, S(CH)2], 4.15–4.19 m [2Н, S(CH)2],
4.29 (Z), 4.54 (Е) br.s (2Н, NН2), 4.42 (Z), 4.79 (Е) s
(2Н, 3-СН2СО), 5.64 (Е), 5.66 (Z) s (1Н, Н5), 6.03–
6.07 m (1Н, NCH), 8.77 (Е), 9.36 (Z) br.s (1Н, NН)
(ratio of Z- and E-isomers 88 : 12%). Found, %: C
44.44; H 5.19; N 20.74. С10Н14N4О3S. Calculated, %:
C 44.71; H 5.11; N 20.89.
3-{2-[5-Hydroxy-3-methyl-5-(4-chlorophenyl)-4,5-
dihydro-1Н-pyrazol-1-yl]-2-oxoethyl}-6-methyl-1-
(thietan-3-yl)pyrimidine-2,4(1Н,3Н)-dione (Vb).
Yield 0.62 g (69%), white crystals, mp 223–225°С
(PrOH). 1Н NMR spectrum (300 MHz), δ, ppm: 2.04 s
(3Н, 3'-СН3), 2.07 s (3Н, 6-СН3), 3.03–3.12 m [4Н,
С4'Н2, S(CH)2], 4.10–4.18 m [2Н, S(CH)2], 4.91 s (2Н,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 5 2014

SYNTHESIS AND STRUCTURE OF HYDRAZONES
715
1
3-СН2СО), 5.61 s (1Н, Н5), 6.00–6.05 m (1Н, NCH),
7.16 s (1Н, 5'-ОН), 7.37 br.s (4Нarom). Found, %: С
53.40; Н 4.78; N 12.56. С20Н21ClN4О4S. Calculated,
%: С 53.51; Н 4.71; N 12.48.
crystals, mp 131–133ºС (i-PrOH). Н NMR spectrum
(300 MHz), δ, ppm: 1.90 (Е,Е'), 1.93 (Е,Z') s (3Н,
=ССН3), 2.09 (Е,Е'), 2.15 (Е,Z') s (3Н, 6-СН3), 2.86 t
(2Н, СН2С6Н5, J 7.7 Hz), 3.08–3.13 m [2Н, S(CH)2],
3.70 t (1Н, СНСО, J 7.5 Hz), 4.15–4.20 m [2Н, S(CH)2],
4.60 (Е,Z'), 4.82 (Е,Е'), 4.87 (Z,Е') s (2Н, 3-СН2СО),
5.67 s (1Н, Н5), 6.04–6.10 m (1Н, NCH), 7.18–7.29 m
(5Нarom), 10.43 (Е,Z'), 10.61 (Е,Е'), 10.79 (Z,Е') br.s
(1Н, NН) (ratio of Е,Z'-, Е,Е'-, and Z,Е'-isomers
15 : 57 : 28%). Found, %: С 56.95; Н 5.39; N 12.65.
С21Н24N4О5S. Calculated, %: С 56.74; Н 5.44; N 12.60.
3-{2-[5-(4-Bromophenyl)-5-hydroxy-3-methyl-
4,5-dihydro-1Н-pyrazol-1-yl]-2-oxoethyl}-6-methyl-
1-(thietan-3-yl)pyrimidine-2,4(1Н,3Н)-dione (Vc).
Yield 0.59 g (60%), yellow crystals, mp 210–211°С
(PrOH). 1Н NMR spectrum (300 MHz), δ, ppm: 2.04 s
(3Н, 3'-СН3), 2.07 s (3Н, 6-СН3), 3.05–3.12 m [4Н,
С4'Н2, S(CH)2], 4.11–4.18 m [2Н, S(CH)2], 4.91 s (2Н,
3-СН2СО), 5.61 s (1Н, Н5), 6.00–6.06 m (1Н, NCH),
7.17 s (1Н, 5'-ОН), 7.31 d (2Нarom, J 7.5 Hz), 7.51 d
(2Нarom, J 7.5 Hz). Found, %: С 48.81; Н 4.23; N
11.27. С20Н21BrN4О4S. Calculated, %: С 48.69; Н
4.29; N 11.36.
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Ethyl-3-(2-{2-[6-methyl-2,4-dioxo-1-(thietan-3-
yl)-1,2,3,4-tetrahydropyrimidin-3-yl]acetyl}-hydra-
zono)butanoate (VIа). Yield 0.55 g (72%), white
1
crystals, mp 127–129ºС (i-PrOH). Н NMR spectrum
(300 MHz), δ, ppm: 1.21 t (3Н, ОСН2СН3, J 7.1 Hz),
1.94 (Е,Е'), 1.96 (Е,Z'), 1.98 (Z,Е') s (3Н, =ССН3),
2.12 (Е,Е'), 2.14 (Е,Z'), 2.17 (Z,Е') s (3Н, 6-СН3), 3.0–
3.13 m [2Н, S(CH)2], 3.35 s (2Н, СН2СО), 4.08–4.20
m [4Н, S(CH)2, ОСН2СН3], 4.62 (Е,Z'), 4.84 (Е,Е'),
4.89 (Z,Е') с (2Н, 3-СН2СО), 5.67 s (1Н, Н5), 6.03–
6.09 m (1Н, NCH), 10.60 (Е,Z'), 10.80 (Е,Е'), 10.91
(Z,Е') br.s (1Н, NН) (ratio of Е,Z'-, Е,Е'-, and Z,Е'-
isomers 17 : 75 : 8%). Found, %: С 50.34; Н 5.82; N
14.71. С16Н22N4О5S. Calculated, %: С 50.25; Н 5.80;
N 14.65.
2-Benzyl-3-(2-{2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-
1,2,3,4-tetrahydropyrimidin-3-yl]acetyl}-hydrazono)-
butanoic acid (VIb). Yield 0.28 g (31%), white
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 5 2014